The present invention relates to treatment of abnormalities in a patient""s vascular system. A specific use of the present invention described below is for the treatment of cerebral aneurysms although the various aspects of the invention described below may also be useful in treating other abnormalities such as arteriovenous malformations (AVM), hypervascular tumors, cavernous carotid fistulas, fibroid tumors, and non-reversible sterilization via fallopial occlusion.
Cerebral aneurysms are enlargements of the cerebral vasculature which protrude like a balloon from the wall of a cerebral artery. The cerebral aneurysm has a neck which leads to the parental vessel and a body or xe2x80x9cdomexe2x80x9d which can vary in diameter from 1-30 mm.
The wall of the aneurysm is often weak and can rupture, leading to hemorrhage. Rupture of the aneurysm can kill the patient or leave the patient with permanent or transitory mental and physical deficits.
Aneurysms are often treated to prevent rupture, leading to hemorrhage, or to prevent rebleeding of acutely ruptured aneurysms. A conventional method of treating aneurysms is to fill the aneurysm with coils. The coils are introduced into the aneurysm one at a time through a delivery catheter until the aneurysm is filled. The aneurysm eventually becomes a solid mass of coils and thrombus.
A problem with the conventional method of using coils to fill aneurysms is that the aneurysm becomes a relatively solid mass due to coils and thrombus contained therein. The mass of coil and thrombus exerts pressure on adjacent areas of the brain which may lead to other problems. Another problem with the conventional method is that the coils must be delivered one at a time into the aneurysm which increases the procedure time and risk to the patient. For large aneurysms, up to twenty coils may be required to fill the aneurysm.
It is an object of the invention to provide improved methods and devices for treating aneurysms. These and other objects of the invention will become evident from the description of the preferred embodiments described below.
In a first aspect of the present invention, a method of treating an aneurysm is provided. An expandable structure is delivered through the vasculature in a collapsed position. Once the expandable structure is at the desired location, such as within a cerebral aneurysm, the expandable structure is expanded. The structure and advantages of the expandable structure are described below. The aneurysm wall is also reduced in size so that the aneurysm does not need to be completely filled in the conventional manner. The expandable shape is sized to be smaller than the aneurysm to permit reducing the size of the aneurysm by at least 30% percent.
A preferred method of reducing the size of the aneurysm is to heat the aneurysmal wall, preferably to a temperature of at least 60xc2x0 and preferably 60-80xc2x0 C., which causes the aneurysmal wall to shrink. The aneurysm may be heated in any suitable manner and preferred methods are monopolar and bipolar RF, laser, microwave, and simple electrical resistance heating. In a preferred method, electrical energy is delivered to the expandable device itself to generate heat. A fluid may be introduced into the aneurysm to prevent clotting during heating and to provide thermal and/or electrical conductance. When using RF heating, for example, the fluid may be saline and more preferably hypertonic saline. Although it is preferred to heat the aneurysmal wall to reduce the size of the aneurysm, the aneurysm may also be reduced in size by chemical action.
The expandable structure forms a matrix of filaments in the expanded condition. The matrix preferably forms a woven or braided structure, however the filaments may also be randomly oriented, parallel, or non-intersection filaments. The matrix may be flexible filaments, such as platinum ribbon, extending randomly, radially or helically within an expandable, permeable, mesh-like enclosure. The material may also be an expandable material such as polymer, nitinol, stainless steel, tungsten or tantalum and alloys/composites thereof The expandable device preferably fills a volume of at least 10% of the aneurysm volume, more preferably at least 40% and most preferably at least 60% of aneurysm volume. The expandable device preferably has internal filaments within the volume to quickly form a stable thrombus. An advantage of the expandable device is that a three-dimensional structure forms without requiring separate delivery of a cage and coils as described in International Application WO 99/07293. In another aspect, the expandable device has a deforming portion which plastically deforms when moving to the expanded position. The deformable portion holds the flexible filaments in the expanded position.
The aneurysm may be reduced in size until the aneurysmal wall contacts the expandable structure so that the expandable structure supports and reinforces the aneurysmal wall. In a particularly advantageous embodiment of the invention, the expandable structure itself is used to transmit energy to heat the aneurysmal wall which causes the aneurysmal wall to fuse to the expandable structure, thereby reinforcing the aneurysmal wall and preventing migration of the expandable structure into the parental vessel.
In another aspect of the invention, the aneurysmal wall may be reduced in size together with the expandable device. In a preferred embodiment, the expandable structure is a soft mesh which easily collapses when the aneurysmal wall is shrunk.
Various optional steps and structure may also be provided. For example, a sealant may be delivered into the aneurysm to ensure that the aneurysm is isolated from the parental artery. An advantage of the present invention is that the sealant is held within a matrix formed by the expandable device which holds the sealant in the aneurysm.
The proximal portion of the expandable structure may be insulated to protect the neck of the aneurysm. The insulation may coat only the flexible filaments so that the structure is still permeable to fluid. Alternatively, the insulation may be impermeable to protect the neck from hot fluid slowly expelled into the aneurysm or to isolate the aneurysm entirely from the parental vessel.
The expandable device may have one or more expandable sections. In an embodiment, the expandable device has two expandable sections wherein energy is delivered to the dome with one of the sections while the second section is insulated to protect the neck.
The expandable device may have a locking mechanism for locking the expandable device in the expanded position. The expandable device is naturally biased toward the collapsed position so that the operator may partially deploy the expandable device to determine whether the device has the appropriate size. If the device does not have the appropriate size, the device is collapsed and removed and another device having the appropriate size is introduced. The locking mechanism is then actuated when the user is satisfied with the size of the device.
In still another aspect of the present invention, a catheter has a cover which is positioned over the neck of the aneurysm to isolate the aneurysm from the parental vessel. The aneurysm is then reduced in size as explained above while the cover isolates the aneurysm. The cover also protects the patient from hemorrhage by isolating the aneurysm from the parental vessel. The cover may be periodically moved to expel heated fluid into the parental vessel when heating and shrinking the aneurysm.
In yet another aspect of the present invention, a coil is used to cover the neck of the aneurysm to regulate the flow of hot fluid out of the aneurysm and into the parental vessel. The pitch of the coil can be varied by the operator during deployment to allow faster or slower leakage of hot fluid out of the aneurysm and into the parent artery during heating.
A catheter is also provided which has a low-impedance coil, such as flat copper ribbon or other suitable material, disposed in the catheter tip. Upon infusion of saline through the catheter and passage of RF energy through the coil, the saline is heated and conducts electrical energy to heat the fluid.
These and other aspects and advantages of the invention will become evident from the following description, drawings and claims.